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  • 1995-1999  (4)
  • Polymer and Materials Science  (3)
  • Key words Birefringence  (1)
  • Glutamate dehydrogenase
  • 1
    Electronic Resource
    Electronic Resource
    Molecular origin of viscoelasticity and chain orientation of glassy polymers (1997)
    Springer
    Rheologica acta 36 (1997), S. 239-244 
    Details
    ISSN: 1435-1528
    Keywords: Key words Birefringence ; stress-optical rule ; chain orientation ; vinyl polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Dynamic birefringence and dynamic viscoelasticity of poly(4-methyl styrene) and poly(4-t-butyl styrene) were measured to investigate the molecular origin of viscoelasticity around the glass transition zone. The data were analyzed with a modified stress-optical rule: The birefringence and the stress were separated into two component functions of different molecular origins. One component is related to the orientation of the main chain axis and the other one to the rotation of the repeating units about the main chain axis. The strain dependence of the two characteristic orientation functions in the glassy zone was estimated and the orientation mechanism of repeating units was discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366664
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  • 2
    Electronic Resource
    Electronic Resource
    Morphology of banded spherulites in poly(ε-caprolactone)/poly(styrene-ran-acrylonitrile) blends (1997)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 48 (1997), S. 354-362 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The occurrence of banded spherulites in blends of poly(ε-caprolactone) with poly(styrene-ran-acrylonitrile) is studied by means of optical-, scanning electron-, environmental scanning electron-, and atomic force-microscopy as well as smallangle X-ray scattering. The measurements reveal that lamellae are confined in fibrils that bend periodically from the center of spherulites in a radial direction. The fibrils show also a regular spacing in the lateral direction. Single bent lamellae can be observed by atomic force microscopy after permanganic etching. The enrichment of amorphous material near to the growth front of the spherulites can be directly observed by polarized light microscopy after temperature jump experiments. The excluded amorphous material on the surface of the growing spherulites has the shape of droplets. This might be the main reason for the initiation of the bending process because the result is a non-uniform stress distribution acting on the growing lamellae at the interface between spherulites and the surrounding melt. The amorphous material of the blends can be found in three areas as observed by small-angle X-ray scattering experiments and microscopical methods: (i) between the lamellae, (ii) excluded from the interlamellar region but within the spherulite, and (iii) for high contents of non-crystallizable material, it can be excluded from the spherulite. The banding periodicity of spherulites as a function of the crystallization temperature can be described in terms of two models, based either (i) on the inherent twisting of lamellae perpendicular to the axis of a screw dislocation or (ii) on the dependence of the diffusion of amorphous material away from the growth front of lamellae and the temperature dependence of the rate of crystallization. Both models fail at very low supercoolings near to temperatures where the banding disappears completely.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1997.010480902
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Evaluation of equation-of-state parameters from PVT data (1995)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 46 (1995), S. 312-318 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The characteristic parameters for three different equation-of-state (EOS) theories have been determined for polystyrene and low-molecular weight polyisoprene using pressure-volume-temperature (PVT) data. Basically two procedures for the calculation of characteristic parameters were applied. The characteristic parameters were calculated, firstly, from coefficients of expansion, compressibilities and densities, and secondly, by fitting the corresponding EOS to PVT data minimizing the sum of the squares of the differences between experimental and calculated pressures. The characteristic parameters obtained by the two methods are compared with regard to their ability to describe PVT data. A comparison of the three different EOS theories reveals that, for describing polymeric liquids, the modified cell model of Dee and Walsh is superior to the theory of Flory, Orwoll and Vrij as well as to the lattice fluid theory of Sanchez and Lacombe. Finally, formulae are given to convert the characteristic parameters from one theory into those of another.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1995.010460405
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Evaluation of equation-of-state parameters and the description of PVT-data (1996)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 47 (1996), S. 520-524 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: For three different equation-of-state theories the characteristic parameters of two polymers were calculated, and the ability of the theories to describe PVT-data using these parameters was investigated. The comparison between the different theories shows that, concerning the description of PVT-data, the modified cell model of Dee and Walsh is not only superior to the theory of Flory, Orvoll and Vrij and that of Sanchez and Lacombe as reported before, but also to the theory of Simha and Somecynsky and the open cell model of Zhong, Wang and Lu. Finally, simple formulae are given to calculate the characteristic parameters of the latter two theories from those of the theory of Flory, Orwoll and Vrij.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1996.010471108
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    Paper (German National Licenses)
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